pthread_rwlock_wrlock(3)

NAME

pthread_rwlock_wrlock, pthread_rwlock_trywrlock - acquire a

read/write
lock for writing

LIBRARY

library ``libc_r'' library ``libpthread'' library ``libthr''

SYNOPSIS

#include <pthread.h>
int
pthread_rwlock_wrlock(pthread_rwlock_t *lock);
int
pthread_rwlock_trywrlock(pthread_rwlock_t *lock);

DESCRIPTION

The pthread_rwlock_wrlock() function blocks until a write

lock can be
acquired against lock. The pthread_rwlock_trywrlock() func

tion performs
the same action, but does not block if the lock cannot be

immediately
obtained.

The results are undefined if the calling thread already

holds the lock at
the time the call is made.

IMPLEMENTATION NOTES

To prevent writer starvation, writers are favored over read

ers.

RETURN VALUES

If successful, the pthread_rwlock_wrlock() and

pthread_rwlock_trywrlock()
functions will return zero. Otherwise an error number will

be returned
to indicate the error.

ERRORS

The pthread_rwlock_trywrlock() function will fail if:

[EBUSY] The calling thread is not able to acquire

the lock

without blocking.

The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock()

functions may
fail if:

[EDEADLK] The calling thread already owns the

read/write lock

(for reading or writing).

[EINVAL] The value specified by lock is invalid.

[ENOMEM] Insufficient memory exists to initialize

the lock

(applies to statically initialized locks

only).

SEE ALSO

pthread_rwlock_init(3), pthread_rwlock_rdlock(3),
pthread_rwlock_tryrdlock(3), pthread_rwlock_unlock(3)

STANDARDS

The pthread_rwlock_wrlock() and pthread_rwlock_trywrlock()

functions are
expected to conform to Version 2 of the Single UNIX Specifi

cation
(``SUSv2'').

HISTORY

The pthread_rwlock_wrlock() function first appeared in

FreeBSD 3.0.

BSD August 4, 1998

BSD